Real-world treatment patterns and mortality associated with GLP1-RAs in breast cancer patients.

629 Background: GLP1 Receptor Agonists (GLP1) are widely used for type 2 diabetes (DM2) and obesity in adults. However, data on modern utilization and associated health outcomes, including all-cause mortality, in breast cancer (BC) patients is limited. We evaluated these endpoints in a BC population from a large US national healthcare database. Methods: Using Truven MarketScan, a commercial insurance claims database which includes over 270 million patients, we extracted eligible invasive BC patients diagnosed between 2014 and 2023 who were ≥ 18 years old, completed definitive BC surgery (index date), received GLP1 for at least 3 continuous months, and had available mortality data. Overall survival (OS) was defined as the time from BC surgery to death from any cause; patients alive at the time of analysis or lost to follow-up were censored at last contact date. Propensity score matching (1:1 ratio) was used to match patients who received GLP1 with those who did not, based on clinical prognostic factors (age; sex; deyo comorbidity index (CI); receipt of immunotherapy, chemotherapy, adjuvant endocrine therapy; DM2; weight category; stroke; myocardial infarction (MI)/coronary artery disease (CAD); heart failure); Kaplan-Meier estimates and log-rank tests were used to compare OS between groups and hazard ratios (HR) were estimated using multivariable Cox proportional hazards models. Results: In 137,493 BC patients, 7,249 (5.3%) received a GLP1 and over half (n=4,019; 55.4%) initiated it after BC surgery. The median follow up time in GLP1 users was 32 (IQR 15-57) months. In GLP1 users the median age was 59 (IQR 53-64) years; 5,860 (80.8%) had DM2 and 1,825 (25.2%) had a CI ≥3; in those with weight data available (n=4,687), 4,609 (98.3%) were in the overweight or obese category. A total of 3,828 (52.8%) received GLP1 concurrent with anti-cancer systemic therapy (chemotherapy, immunotherapy, or adjuvant endocrine therapy). The median duration of GLP1 use was 2.1 (IQR 0.8-6.1) years. GLP1 use increased over time (3.2% in 2014, 5.2% in 2018, 7.2% in 2023). Semaglutide was the most common agent prescribed across all years (35.8%) and exhibited the greatest annual increase in use after 2018. In the propensity score matched cohort, OS was significantly higher in GLP1 users vs non-users (n=7,248 per group): 5 year OS 95.8% GLP1 vs. 89.5% non-users (adjusted HR 0.41, 95% CI: 0.34-0.49, p<0.001). Conclusions: We describe one of the largest observational studies on real-world GLP1 prescription patterns and associated mortality in a BC cohort. Use of these agents is increasing over time in BC patients. Our research supports other emerging epidemiologic data suggesting a potential all-cause mortality benefit with these incretin mimetics in this population. Prospective studies are warranted to clarify the biological mechanisms underlying this association, including metabolic health implications and effects on BC tumor biology.